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CRRAB II > Potassium > Flashcards

Potassium Flashcards

1
Q

Cellular functions of K+:

A

protein and glycogen synthesis

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2
Q

Normal extracellular K+:

A

4-5 meq/L

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3
Q

Electrical function of K+:

A

maintains resting membrane potential

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4
Q

Sx of low or high K+:

A

cramps

muscle weakness/paralysis

EKG changes/arrhythmias

**relates to the inability of muscles to generate action potentials

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5
Q

EKG changes in hyp-O-kalemia:

A

PR prolongation

ST depression

flattened or inverted T wave

U waves (right after T wave)

QRS widening

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6
Q

EKG changes in hyp-ER-kalemia:

A

PR prolongation

ELEVATED T waves

widened QRS

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7
Q

What increases threshhold potential and protects against the decreased resting potential of hyp-ER-kalemia?

A

hypercalcemia

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8
Q

Releases K+ from cells in exchange for HCl buffering, exacerbating hyperkalemia?

A

metabolic acidosis

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9
Q

Hypokalemia _______ digoxin toxicity but hyperkalemia ______ digoxin toxicity.

A

increases

causes

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10
Q

Molecules that move K+ into cells:

A

insulin

catecholamines

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11
Q

How do insulin and catecholamines get K+ into cells?

A

increased activity of Na-K-ATPase

increase uptake in skeletal muscle and liver

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12
Q

Acidemia effect on serum K+:

A

Increases as H+ is buufered in to cells

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13
Q

Alkalemia effect on serum K+:

A

Decrease as H+ is buffered into extracellular fluid

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14
Q

If K+ lost in stool or sweat is clinically relevant?

A

Pathologic

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15
Q

Major route of K+ elim?

A

Kidney

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16
Q

Determinants of K+ secretion by kidney:

A

plasma concentration

urine flow in distal tubule

ALDOSTERONE: K+ secretion by PRINCIPAL cells of collecting tubule

17
Q

How does K+ get reabsorbed in loop of Henle?

A

NKCC pump

18
Q

How can K+ get reabsorbed during severe hypokalemia?

A

Intercalated cells in collecting tubule

alpha cells – K+/H+ antiporter

19
Q

Distal tubule secretion of K+ involves?

A

Principal cells

  • luminal Na+ and K+ channels
  • basolateral Na-K-ATPase

ALDOSTERONE

  • very sensitive to K+ change (responds to 0.1 meq increase)
  • increases Na and K channels
  • increases activity of NA-K-ATPase

K conc gradient

distal flow is permissive??

20
Q

Causes of hyp-O-kalemia:

A

decreased intake (rare)

increased entry into cells (acidemia)

increased GI loss

increased urinary loss

increased sweat loss

dialysis

21
Q

Dietary phenomena that binds K+ leading to hypokalemia?

A

Clay ingestion

22
Q

Three causes of hypokalemia due to increased cellular uptake:

A

metabolic acidosis

hyperinsulinemia

increased catecholamines

23
Q

Causes of hypokalemia due to increased urinary loss?

A

Increased distal flow due to impaired salt and water reabsorption

  • diuretics
  • salt wasting nephropathies
  • polydypsia/polyuria

Hypercalcemia

Mineral corticoid excess (Aldosterone)

Hypomagnesemia (effects K channels)

24
Q

How would you determine if K loss was due to kidney?

A

24 hour urine K+ test

if low –> not kidney problem

25
Q

If you have a low urinary K (GI loss) and acidemia, what part of GI tract is responsible?

A

Lower GI (laxatives, cancer)

26
Q

If low urinary K (GI loss) and alkalemia, what part of GI tract is responsible?

A

Upper (vomiting)

27
Q

If K loss is kidney related with acidemia, what are the possible problems?

A

ketoacidosis

type I or II renal tubular acidosis

28
Q

If K loss is kidney related and alkalemia is present in a normotensive patient, what could the problem be?

A

vomiting

diuretics (early)

Bartter’s syndrome (inherited)

29
Q

Hypertensive alkalosis due to kidney loss of K with high renin could be from:

A

diuretics

renovascular disease

reninoma

Cushings

30
Q

Hypertensive alkalosis due to kidney loss of K with low renin could be from:

A

low aldosterone (or high???)

31
Q

Drugs that can cause hyperkalemia in the setting of normal total body K:

A

succinylcholine

beta blockers

digoxin

32
Q

Most common cause of hyperkalemia:

A

renal failure

33
Q

Major hormone responsible for renal excretion of K?

A

Aldosterone

34
Q

First thing to do to treat hyperkalemia?

A

Calcium IV

35
Q

Second things to do to get K into cells in Hyperkalemia?

A

Glucose and insulin

NaHCO3

Beta-agonist (albuterol nebs)

3% NaCl if hyponatremic

36
Q

Long term(ish) treatment (hours) for hyperkalemia:

A

loop diuretics

cation exchange (kayexalate)

dialysis

CRRAB II (28 decks)

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